The nested javac task behaves more or less as documented for the top-level javac task. srcdir, destdir, classpath, encoding for the nested javac task are taken from the enclosing groovyc task. If these attributes are specified then they are added, they do not replace. In fact, you should not attempt to overwrite the destination. Other attributes and nested elements are unaffected, for example fork, memoryMaximumSize, etc. may be used freely.

Joint Compilation

Joint compilation means that the Groovy compilation will parse the Groovy source files, create stubs for all of them, invoke the Java compiler to compile the stubs along with Java sources, and then continue compilation in the normal Groovy compiler way. This allows mixing of Java and Groovy files without constraint.

To invoke joint compilation with the jointCompilationOptions attribute, you have to simulate the command line with compiler switches. -j enables the joint compilation mode of working. Flags to the Java compiler are presented to the Groovy compiler with the -F option. So, for example, flags like nowarn are specified with -Fnowarn. Options to the Java compiler that take values are presented to the Groovy compiler using -J options. For example -Jtarget=1.4 -Jsource=1.4 is used to specify the target level and source level. So a complete joinCompilationOptions value may look like: "-j -Fnowarn -Jtarget=1.4 -J-source=1.4". Clearly, using this way of specifying things is a real nuisance and not very Ant-like. In fact there are thoughts to deprecate this way of working and remove it as soon as is practical.

The right way of working is, of course, to use a nested tag and all the attributes and further nested tags as required. It is rare to specify srcdir and destdir, the nested javac task is provided with the srcdir and destdir values from the enclosing groovyc task, and it is invariable the right thing to do just to leave this as is. Here is an example:

To restate: the javac task gets the srcdir, destdir and classpath from the enclosing groovyc task.